Andy's attempt to create a reasonable descriptive model of ME.

Exactly, so that is why Andy's 30 level for basal metabolic rate seems not too far off!

 

I think we are getting in a muddle here?

Most of the body's energy production goes to sustaining itself in the average lazy modern person. But that same person, if suddenly finding themselves having to flee a war for a week could expend twice as much energy as their normal total. So the 'ability to produce energy' is way above the level normally produced. Cut the ability to produce energy by a small amount and nobody would notice, unless of course they were fleeing a war.

So the decrease in ability to produce energy in ME must be huge.

 

No, I think we have finally realised we completely agree.

 

So I guess the question is why are Day 1 CPET results pretty normal?

 

Must it be huge? What about for those very mildly affected, who are likely to be undiagnosed. I went for years, feeling awful but still holding down a full-time job that included a 90 min round trip commute at one stage - in requiring a 50% (or whatever large percentage is required) drop in functioning this group will be excluded. I worry the fact that forum members will tend to be more severely affected is strongly influencing many comments on this issue.

 

Because we have an abnormal reaction to overexertion that tends to have a delayed onset?

 

The trouble for me is that I cannot see a plausible metabolic model that would work like this. It seems as if once fully 'recuperated' ME muscles can generate the same energy as in normal sedentary people. That would suggest a metabolic problem involving some sort of defect in restocking short term energy stores. If so I would expect the effort of just basic activities for PWME to lead to some depletion of stock pretty much all the time.

I also think that a metabolic shift in muscle tissue lasting for hours should have been reasonably easy for the physiologists to pick up with magnetic resonance spectroscopy thirty years ago.

Another point is that is it is a local metabolic problem with depletion of energy stores in used tissues then there should be no problem doing other things, as I mentioned on one of these threads earlier. If you deplete energy in right arm muscles there should be no effect on left leg muscles.

 

I don't believe that the average healthy person would be able to do those things and not feel any effect at all, as those are things the average healthy person does. My model would argue that they have a higher tolerance for those ill effects that they will feel (tired, maybe sore and stiff), and that the responsive biological mechanism to over-exertion, that in patients results in PEM, will kick in correctly for that person and if they continue to regularly repeat those additional things will result in higher fitness for them i.e. a higher SEL.

ETA: Changed wouldn't to would in "I don't believe that the average healthy person would be able to do those things and not feel any effect at all"

 

I am constantly going from "a little bit of spare energy" to "exhausted" despite already reduced activity levels.

Maybe there are two problems. One is a relatively minor energy production issue that produces short term effects in the timeframe of hours and this makes patients think that they have an energy production problem. Another problem is something that occurs in the timeframe of days and produces PEM.

 

Yes. I prefer to make a distinction between the (muscle) fatiguability which is short term and PEM which is more like a payback mechanism over a couple of days.

Personal note: I get this lactic acid like feeling (the feeling that you have just run a marathon) in my muscles after even minor physical activities and I had this at the beginning of my illness when I was 100% sure it couldn't be due to deconditioning. The weird thing is that my muscle function is pretty much fine until that lactic acid like feeling prematurely kicks in. So I can sprint pretty fast for say approximately 40 meters but cannot go for a simple walk with my family during holidays. So it seems like an issue of endurance. Sorry for this digression - I may be an exception or a part of a subgroup in this. Just added it because it is an abnormal response to exercise that isn't really covered under PEM. Perhaps it could also explain the seemingly normal CPET 1 that Jonathan mentioned - I would prefer to see a test of (muscle) endurance that isn't hard or intensive but takes more than 30 minutes.

 

I've tried to rephrase the text a little in accordance with my own view and what has been said and commented. I apologise in advance to Andy if this isn't the direction he wants it to go:


Sustainable exertion limit (SEL)
ME patients have a reduced sustainable exertion limit and an abnormal reaction to overexertion. Both are individual to each patient and may change over time.

Sustainable exertion limit (SEL) refers to the maximum energy expenditure that can be sustained and replicated without overexerting. Everyone has a SEL, but in patients with ME this limit is considerably reduced.

Persons can temporarily exert themselves above their SEL. What happens then is determined by their tolerance to overexertion. In patients with ME this tolerance to overexertion is significantly reduced. The price ME patients pay for overexertion is higher than for healthy persons.

Post-exertional malaise (PEM)
Too much overexertion results in an increase of ME-related symptoms, commonly referred to as post-exertional malaise (PEM). During PEM, patients with ME not only experience an increase in disability but also a lowering of their SEL. This means that previously sustainable energy expenditure may now cause additional overexertion. As a result, ME patients often have to reduce their activity level to recover from PEM and avoid their condition from getting worse.

Counterbalance with rest
Moderately ill ME patients may have a SEL that is reduced by 50% compared to healthy persons. They are unlikely to be working full time, but may overexert themselves for one or two days to keep up with professional or social activities to the best of their ability. Consequently, patients have to include extra rest periods during the week to avoid PEM. As long as the reduction in activity during the other days is sufficient to counterbalance the overexertion, this activity pattern may be sustainable.

In patients with severe ME the SEL may become close to average basal metabolic rate, meaning that even basic activities such as showering or toileting could cause overexertion and PEM.

Implications

Due to a lowered SEL and tolerance to exertion, the mechanism by which increased activity leads to fitness in healthy persons may be defunct in patients with ME.

Overexertion and PEM may be a reason why some ME patients deteriorate over time, although there are reports from patients of declines despite avoiding overexertion to the best of their abilities.

Similar to Delayed Onset Muscles Soreness (DOMS), ME patients frequently report a delayed onset of PEM, starting several hours or longer after overexertion.

 

Dr Myhill's proposed mechanism:
https://drmyhill.co.uk/wiki/CFS_-_The_Central_Cause:_Mitochondrial_Failure

 

Interestingly... For some PWME, what you are talking about is the case, i.e. tiring yourself out in one muscle area leads to PEM in the whole body. But for some PWME, including myself, it will usually only lead to PEM in that particular muscle area. It is quite common for me to say "I have PEM in my arms at the moment" for example. I only get full-body PEM if I overexert myself in a cardiac sense (too much time with a high heart rate). And I get cognitive PEM if I overexert myself cognitively.

You might be interested in my PEM Polls which I ran a couple of months ago on S4ME.